/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.sockjs.client;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.lang.Nullable;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.SettableListenableFuture;
import org.springframework.web.client.HttpServerErrorException;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.sockjs.frame.SockJsFrame;
import org.springframework.web.socket.sockjs.transport.TransportType;

import java.net.URI;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * Abstract base class for XHR transport implementations to extend.
 *
 * @author Rossen Stoyanchev
 * @since 4.1
 */
public abstract class AbstractXhrTransport implements XhrTransport {

    protected static final String PRELUDE;

    static {
        byte[] bytes = new byte[2048];
        for (int i = 0; i < bytes.length; i++) {
            bytes[i] = 'h';
        }
        PRELUDE = new String(bytes, SockJsFrame.CHARSET);
    }


    protected final Log logger = LogFactory.getLog(getClass());

    private boolean xhrStreamingDisabled;


    @Override
    public List<TransportType> getTransportTypes() {
        return (isXhrStreamingDisabled() ? Collections.singletonList(TransportType.XHR) :
                Arrays.asList(TransportType.XHR_STREAMING, TransportType.XHR));
    }

    /**
     * Whether XHR streaming is disabled or not.
     */
    public boolean isXhrStreamingDisabled() {
        return this.xhrStreamingDisabled;
    }

    /**
     * An {@code XhrTransport} can support both the "xhr_streaming" and "xhr"
     * SockJS server transports. From a client perspective there is no
     * implementation difference.
     * <p>Typically an {@code XhrTransport} is used as "XHR streaming" first and
     * then, if that fails, as "XHR". In some cases however it may be helpful to
     * suppress XHR streaming so that only XHR is attempted.
     * <p>By default this property is set to {@code false} which means both
     * "XHR streaming" and "XHR" apply.
     */
    public void setXhrStreamingDisabled(boolean disabled) {
        this.xhrStreamingDisabled = disabled;
    }


    // Transport methods

    @Override
    public ListenableFuture<WebSocketSession> connect(TransportRequest request, WebSocketHandler handler) {
        SettableListenableFuture<WebSocketSession> connectFuture = new SettableListenableFuture<>();
        XhrClientSockJsSession session = new XhrClientSockJsSession(request, handler, this, connectFuture);
        request.addTimeoutTask(session.getTimeoutTask());

        URI receiveUrl = request.getTransportUrl();
        if (logger.isDebugEnabled()) {
            logger.debug("Starting XHR " +
                    (isXhrStreamingDisabled() ? "Polling" : "Streaming") + "session url=" + receiveUrl);
        }

        HttpHeaders handshakeHeaders = new HttpHeaders();
        handshakeHeaders.putAll(request.getHandshakeHeaders());

        connectInternal(request, handler, receiveUrl, handshakeHeaders, session, connectFuture);
        return connectFuture;
    }

    protected abstract void connectInternal(TransportRequest request, WebSocketHandler handler,
                                            URI receiveUrl, HttpHeaders handshakeHeaders, XhrClientSockJsSession session,
                                            SettableListenableFuture<WebSocketSession> connectFuture);


    // InfoReceiver methods

    @Override
    public String executeInfoRequest(URI infoUrl, @Nullable HttpHeaders headers) {
        if (logger.isDebugEnabled()) {
            logger.debug("Executing SockJS Info request, url=" + infoUrl);
        }
        HttpHeaders infoRequestHeaders = new HttpHeaders();
        if (headers != null) {
            infoRequestHeaders.putAll(headers);
        }
        ResponseEntity<String> response = executeInfoRequestInternal(infoUrl, infoRequestHeaders);
        if (response.getStatusCode() != HttpStatus.OK) {
            if (logger.isErrorEnabled()) {
                logger.error("SockJS Info request (url=" + infoUrl + ") failed: " + response);
            }
            throw new HttpServerErrorException(response.getStatusCode());
        }
        if (logger.isTraceEnabled()) {
            logger.trace("SockJS Info request (url=" + infoUrl + ") response: " + response);
        }
        String result = response.getBody();
        return (result != null ? result : "");
    }

    protected abstract ResponseEntity<String> executeInfoRequestInternal(URI infoUrl, HttpHeaders headers);


    // XhrTransport methods

    @Override
    public void executeSendRequest(URI url, HttpHeaders headers, TextMessage message) {
        if (logger.isTraceEnabled()) {
            logger.trace("Starting XHR send, url=" + url);
        }
        ResponseEntity<String> response = executeSendRequestInternal(url, headers, message);
        if (response.getStatusCode() != HttpStatus.NO_CONTENT) {
            if (logger.isErrorEnabled()) {
                logger.error("XHR send request (url=" + url + ") failed: " + response);
            }
            throw new HttpServerErrorException(response.getStatusCode());
        }
        if (logger.isTraceEnabled()) {
            logger.trace("XHR send request (url=" + url + ") response: " + response);
        }
    }

    protected abstract ResponseEntity<String> executeSendRequestInternal(
            URI url, HttpHeaders headers, TextMessage message);

}
